1. Field of the Invention
The present invention relates to balancing machines and support structures usable with balancing machines. More particularly, the invention provides a balancing machine that has support structures with upper portions interconnected with each other during a first type of balancing operation, the upper portions being movable with respect to each other during a second type of balancing operation.
2. Description of the Prior Art
Due to production flow requirements or quality assurance of electric motors for hand tools or appliances, it often is necessary to balance rotors for these motors using their own ball or sleeve bearings located between commutator and fan. For convenience of assembly, non-rotating parts are put on the rotor prior to balancing. These loose-hanging parts, usually behind the bearing on the armature, have to be held in place while balancing, without influencing the balancing measurements.
In the past, balancing of such rotors required use of flexible spring-loaded saddle bearings, as described in U.S. Pat. No. 3,159,435, or bearing-loaded bearings, as described in U.K. 2,037,445, such bearings being positioned on top of work supports. In such saddle bearings, cradles have been used to connect saddles with each other or two-plane measuring tables supported by three of more round springs, with two built-in force measuring pick ups in each end, have been used. One type of the first mentioned kind of balancer uses two rigid load cells, such as piezo crystal force transducers, or semi-rigid work supports with displacement or velocity type pick ups or transducers to measure remaining vibrations, as described in U.S. Pat. No. 3,182,511.
In flexible or self-aligning saddle bearings, cradles are usually used to connect these saddle bearings with each other to accommodate the rotors in their own bearings. Supports of the type described in U.S. Pat. No. 3,159,159 and U.K. 2,037,445 have been used to compensate for a bend in the rotor shaft (axis of shaft skewed to axis of rotor) or lack of perpendicularity between bearings attached to the shaft and the shaft axis. One disadvantage of spring-loaded saddle bearings of the type described in U.S. Pat. No. 3,159,435 is unavoidable resonances during rotation of the rotor as part of a balancing operation. Bearing-loaded saddle bearings of the type described in U.K. Pat. No. 2,037,445 must overcome frictional forces at the start of a balancing operation and cannot be used to measure small amounts of unbalance. Saddle bearings are expensive and unreliable on a balancing machine. Balancing machines using measuring tables supported by three or more round springs are limited by the size of the table as to the size of the rotor that can be balanced.